Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$232.34	4.575%	$242.9696	$242.97	$242.95	$243.00
Purchase #2	$150.29	7.823%	$162.0472	$162.05	$162.05	$162.00
Purchase #3	$14.34	5.113%	$15.0732	$15.07	$15.05	$15.10
Purchase #4	$121.55	8.303%	$131.6423	$131.64	$131.65	$131.60
Purchase #5	$145.27	10.295%	$160.2255	$160.23	$160.25	$160.20
Purchase #6	$59.83	11.460%	$66.6865	$66.69	$66.70	$66.70
Purchase #7	$35.89	13.114%	$40.5966	$40.60	$40.60	$40.60
7 purchase totals =	$759.51		$819.2409	$819.25	$819.25	$819.20